Its \(K_0\)  is called the preprojective KHA of \(Q\) . A \(\mathbb {C}^*\) -equivariant version is conjectured [1]} to be the positive part of the Okounkov–Smirnov quantum affine algebra \(U_q\left(\widehat{\mathfrak {g}_Q}\right)\)  [2]}. There is also a preprojective CoHA of \(Q\)  [3]}, [4]}, and a \(\mathbb {C}^*\) -equivariant version is conjectured [5]} to be the positive part of the Maulik–Okounkov Yangian \(Y_{\text{MO}}\left(\mathfrak {g}_Q\right)\)  [6]}.
